Losses caused by collision are to be borne as follows:

1. (a) If either party was exclusively in fault he shall bear his own loss, and he shall compensate the other for any loss he has sustained.
2. (b) If neither was in fault, the loss shall be borne by him upon whom it falls.
3. (c) If both were in fault, the loss shall be equally divided, unless it appears that there was a great disparity in fault, in which case the loss shall be equitably apportioned.
4. (d) If it can not be ascertained where the fault lies, the loss shall be equally divided.